S. Muller

PARP-2, A Novel Mammalian DNA Damage-dependent Poly(ADP-ribose) Polymerase

Poly(ADP-ribosylation) is a post-translational modification of nuclear proteins in response to DNA damage that activates the base excision repair machinery. Poly(ADP-ribose) polymerase which we will now call PARP-1, has been the only known enzyme of this type for over 30 years. Here, we describe a cDNA encoding a 62-kDa protein that shares considerable homology with the catalytic domain of PARP-1 and also contains a basic DNA-binding domain. We propose to call this enzyme poly(ADP-ribose) polymerase 2 (PARP-2). The PARP-2 gene maps to chromosome 14C1 and 14q11.2 in mouse and human, respectively. Purified recombinant mouse PARP-2 is a damaged DNA-binding protein in vitro and catalyzes the formation of poly(ADP-ribose) polymers in a DNA-dependent manner. PARP-2 displays automodification properties similar to PARP-1. The protein is localized in the nucleusin vivo and may account for the residual poly(ADP-ribose) synthesis observed in PARP-1-deficient cells, treated with alkylating agents or hydrogen peroxide.

Antigenic properties and protective capacity of a cyclic peptide corresponding to site A of influenza virus haemagglutinin

Two cyclic peptide analogues corresponding to residues 139-146 (site A) of influenza A virus haemagglutinin (strain X31) were synthesized. The ability of these peptides to react with anti-influenza virus antibodies was found to depend on the conformation of the loop and on the orientation in which the peptide was presented to antibodies. Antibodies raised to the peptides were able to bind in ELISA with influenza virus antigen that had been allowed to dry on the microtitre plate. When OF1 mice were immunized with cyclic peptides, approximately 80% of the animals were protected against an intranasal challenge with influenza virus.

Recognition of synthetic peptides of Sm-D autoantigen by lupus sera

The reactivity of autoantibodies present in the serum of patients with systemic lupus erythematosus (SLE) was investigated by ELISA using seven overlapping synthetic peptides representing the entire sequence of the polypeptide D component of ‘Sm antigen’. Of the 165 SLE sera tested, 59% were found to contain IgG antibodies able to bind to peptide 1–20, while 37% of the sera reacted with peptide 44–67. All sera reacting with peptide 44–67 also reacted with peptide 1–20. These two peptides were only seldom recognized by the sera of 187 patients with other rheumatic autoimmune diseases or by 53 sera of normal individuals. In a parallel study using sera that reacted with the D band in immunoblotting, most of the sera recognized peptides 44–67 (89%) and 1–20 (67%), while 33% of them reacted with peptide 97–119. The use of these synthetic peptides in ELISA may be of considerable help for detecting anti Sm autoantibodies.

The Role of Post Synthetic Histone Modifications on Chromatin Conformation: an Immunochemical Study

Abstract Polyclonal and monoclonal antibodies specific for histones as well as sera directed against synthetic peptides of histones were used to probe the topography of chromatin subunits and to monitor conformational alterations induced by post synthetic modifications of histones. Acetylation, phosphorylation and poly ADP-ribosylation of histones were found to affect the surface accessibility of various histone fragments.